Signaling system for railroads



W. H. REICHARD SIGNALING sYsTEM FOR RAILROADS June 28, 1938.

3 Sheets-Sheet 1 Filed April 10, 1935 ATTORNl EY June 8- w. H. REICHARDSIGNALING SYSTEM FOR RAILROADS Filed April 10, 1935 5 Sheets-Sheet 2INVENTOR BY 1W?!- AQ /L; ATTORN'EY o2 "Ax Il-N-CI June 28, 1938. w. H.REICHAR D v SIGNALING'SYSTEM FOR RAILROADS Filed April 10, 1935 3Sheets-Sheet 3 ATTORNE Patented June 28, I938 PATENT OFFICE SIGNALINGSYSTEM FOR RAILROADS Wade H. Reichard, Rochester, N. Y., assignor toGeneral Railway Signal Company, Rochester,

Application April 10, 1935, Serial No. 15,645

11 Claims.

This invention relates to systems for signaling for railroads of theso-called coded track circuit type, in which intermittent energizationof the track rails with impulses having distinctive 5." codecharacteristics is employed to operate track relays and suitabledecoding equipment to control the indications of the wayside signalsand/or cab signals for train control equipment on locomotives.

In this co-called coded track circuit type of system, the intermittentenergization of a track relay is required to display a proceed, orcaution, or approach restrictive wayside signal indication; and it hasbeen proposed to employ coding and decoding devices of such design andconstruction that their various moving parts and contact means areadapted for continuous operation. It can be seen, however, that it isnot necessary to have the coding and decoding equipment in operation togive proceed indications for the wayside signals, or provide coded railcurrent to control cab signal or train control apparatus on locomotives,unless a train is present to take advantage of the wayside or cab signalindications; and since railroad tracks are usually occupied by trainsonly a relatively small percentage of the time, it is apparent thatthere is a great deal of wear and deterioration of contacts and movingparts of the coding and decoding equipment which is ungo necessary ifthis equipment is operating continuously.

In accordance with this invention, generally speaking, it is proposed toprovide a system of coded track circuit control in which the coding 35.and decoding equipment is normally inactive, but is automatically setinto operation when a train approaches, thereby avoiding unnecessarywear and deterioration of the moving parts and contacts of theapparatus.

In accordance with this invention, it is also proposed to provide anorganization of thermionic devices of the usual vacuum tube type in thedecoding apparatus in lieu of a code following track relayintermittently opening and closing its con- 45. tacts, thereby avoidingthe disadvantages and difficulties associated with contacts and devicesoperating at relatively high rates and with the relatively small amountof current available in the track circuit.

Other characteristic features, attributes, and advantages of theinvention will be in part apparent and in part pointed out as thedescription progresses.

In the accompanying drawings, Fig. 1 illus- 55 trates in a simplifiedand diagrammatic manner one specific embodiment of the invention toprovide approach control of the coding equipment; Fig. 1A is anexplanatory diagram of parts of the same equipment to illustrate thecondition of the various parts upon the approach of a train; and Fig. 2shows the modified construction of the decoding apparatus involvingvacuum tubes and no constantly moving parts.

Referring to Fig. 1, the trackway apparatus is illustrated for one blockor track section 3, and for the ends of two adjacent blocks 2 and 4. Itis contemplated that this equipment will be the same for each block; andfor convenience the corresponding relay and devices for the severalblocks shown are designated by the same reference letter with adistinctive suffix number. The track rails B are bonded together anddivided by insulated joints 1 into track sections in the usual way, itbeing assumed that each track section will extend one block length. Itis also contemplated that a wayside signal of any suitable type will belocated at the entrance end to each block. As illustrated, it is assumedthat this wayside signal will be of a typical color light signal, havinglamps to be lighted to display the usual green (G), yellow (Y) and red(R) indications.

At the exit end of each block, traffic being from left to right asindicated by the arrow, the secondary of a transformer 8 is connectedacross the track rails; and the primary of this transformer is arrangedto be energized with a steady or coded alternating current, preferablyof a distinctive frequency such as 100 cycles, which may be obtainedfrom any suitable source, in this instance assumed to be a transmissionline 9 energized from a suitable generator G. At the entrance end toeach block is the code following track relay T, which is assumed to be adirect current tractive type relay of the usual construction, and whichis connected across the track rails through a double-wave rectifier l0of the usual construction. This track relay T is intermittently orsteadily energized in accordance with the supply of alternating currentto the track rails at the exit end of the block, and is employed tocontrol the operation of suitable decoding apparatus to close contactsselectively in accordance with the code being transmitted.

In the simplified embodiment of the invention illustrated, the code forthe rail current is assumed to be of the simple rate type, in which thecode character depends upon the rate or periodicity in which the railcurrent is supplied to the track rails. For convenience in explanationand by way of illustration, it is assumed that the -of track relay TI(see Fig. 1A).

code rate for a clear or proceed indication will be 180 impulses perminute, and for the caution indication 75 impulses per minute, a stopindication corresponding with steady rail current or absence of railcurrent. The type of decoding equipment shown comprises a transformerhaving a primary I I with a midtap connected to one terminal of asuitable source of direct current indicated conventionally by the symbolminus The opposite terminals of this primary II are connected to theother terminal of said source of current through front and back contactsof the armature or contact finger 43 of the code following track relayT. Two secondaries I2 and I2 of this transformer, the secondary I2 beingconnected through a suitable condenser I3, and with additionalreactances if necessary, are connected to double-wave rectifiers I4 andM which in turn supply current to two direct current relays designatedRI and R15.

The operation of this decoding apparatus, governed by the code followingtrack relay T, is similar to the decoding apparatus on the locomotiveshown and described, for example, in the patent to Wm. D. Hailes, No.1,852,409, April 4, 1932. The energization and de-energization of thecode following track relay T energizes the primary ii of the transformerwith direct current, first in one direction and then in the otherdirection, thereby inducing in effect alternate voltages in thesecondaries I2 and I2 of a periodicity or frequency corresponding withthe code rate at which the relay T is operating; and the relativeinductive and capacity reactance of the circuits of the secondaries I2and I2 of the transformer are so selected that effective energizingcurrent is supplied to the relay R15 when the code rate is 75 and to therelay RI80 when the code rate is 180.

The decoder relays R15 and RIBB control circuits, readily traced on thedrawings, for lighting the lamps of the wayside signal, so as to lightthe lamp G when relay RIBU is energized, lamp Y when relay R15 isenergized and RI80 de-energized, and the lamp B. when both relays aredeenergized.

Associated with eachblock is a modulator or coder having contacts forintermittently opening and closing the circuit for energizing theprimary of the track transformer 8. Such modulator or coder may takevarious forms; and for simplicity, it is assumed that such coder willcomprise a suitable motor M, of a constant speed type, preferably apolyphase or synchronous motor, which operates contacts designated C15and CIBU. The energizing circuit for the coder motor M is shownconventionally with its terminals BX and CK.

Considering now the means for providing the approach controlcharacterizing this invention, at the exit end of each block is anapproach control relay A, arranged to be energized over a line circuitif the track relay T of the corresponding block, or if either of thenext two blocks in the rear thereof, is de-energized. For example, theapproach control relay A3 at the end of the block 3 is energized by'aline circuit starting at a common wire, indicated by the symbol C,through the relay A3, line wire I? through back contact I8 of trackrelay T3, to a suitable source of direct current, designated by thesymbol and thence back over the common wire, or over the line wires Hand I9 through the back contact 23 of track relay T2 to or through theadditional line wire 2| through the back contact 22 Each approachcontrol relay A, when energized, supplies current to the correspondingcoder M to initiate operation of the coder at the end of that block.

Considering the operation, the parts are shown in Fig. 1 in the normalcondition. The approach relays A2 and A3 are de-energized; and the trackrails of each block are steadily energized through the track transformer8 by a circuit for its primary which in the case of block 3 may betraced from the lower transmission line wire 9, wire 25, primary oftransformer 23, wires 26, 21, 28, through the back contact 29 of theapproach control relay A3, and wire 30 back to the other transmissionline wire. The code following track relays T are thus steadilyenergized; and the decoder relays R15 and RI 811 are de-energized,lighting the lamps R at each signal. The approach relays beingdeenergized, the coders are not operated. In short,

the decoding equipment is inactive and at rest, the signals indicatestop, and the track circuits are steadily energized.

Assuming now that a train approaches and enters the block I, the partsassume the condition i1- lustrated in Fig. 1A. The train X shunts thetrack relay TI in the usual way, closing its back contact I8 to energizeapproach relay AI, back contact 2% to energize relay A2, and backcontact 22 to energize relay A3. The energization'of these approachcontrol relays starts the coders at the ends of blocks I, 2, and 3. Theenergization of the approach control relay A3 breaks at its back contact29 the circuit for normally supplying current to the primary of thetransformer B, and closes a circuit through Wire 3i, back contact 32 ofrelay R15 for the block 4, wire 33, back contact 34 of relay RISK wire35, contact C15 for coder M3 and wires 36, 2? and 26 to the primary ofthe transformer 8, and wire 25 back to the transmission line. Thus,impulses at the 75 coderate are supplied to the track rails at the endof the block 3, and the track relay T3 starts to operate at the 75 coderate. This picks up the decoder relay R75, establishing a circuit forsupplying rail current to the block 2 through the front contact 32 ofrelay R15, wires 31 and 38, through the contacts Clti. Consequently, therail current supplied to block 2 is. at the code rate, and thisenergizes the decoder relay RI 8!] for that block, closing its frontcontact 34 to connect the contacts CIfi-B into the circuit for supplyingrail current to the block I.

In this manner, upon the approach of a train as X, the coders areautomatically started for two blocks ahead; and assuming no trainspresent, the track relays and decoder relays are operated in such amanner as to display a proceed or green indication at the entrance tothe next block, a caution or yellow indication at the next block inadvance, with a red or stop indication at the next block still furtherahead. Also, rail current at the 180 code rate is supplied to the blockI in which the train X is located, so that suitable decoding equipmenton this train, such as disclosed in the I-Iailes patent above mentioned,will respond and establish proceed conditions on the locomotive.

As the train advances, the approach relay for the next block 4 isenergized, starting the coder for that block and changing the code ratesfor the blocks in the rear; and as the train progresses, the sameoperation is repeated.

If one of the blocks ahead'is occupied, as for example the block 4, thetrack relay T4 for that block is shunted and cannot respond to the codedrail current, even when the coder'for that block'is started; and a stopindication is maintained at that entrance to that occupiedblock, with acaution indication in the next block in the rear. 7

From the foregoing it can be seen that there is provided by thisinvention a system of coded track circuit control in which the codingand decoding equipment is normally inactive, but is automaticallystarted into operation an appropriate distance ahead of an approachingtrain, so that this train receives proceed indications so long as thetrack is unoccupied and will receive the appropriate caution and stopindications as it approaches an occupied block. A system for threeindications has been illustrated; but it is apparent that the sameprinciples and organiza- I tionof means may be extended to provide forfour or more indications.

In the arrangement shown in Fig. 1, the proper signal indication andcontrol of rail current to the block in the rear is dependent upon therate at which the track relay T operates its armature to open and closeits front and back contacts. In other words, the armature of the trackrelays T will be moving at rates of 75 or 180 times per minute while thesystem is operating; and even if approach control means is employed asabove explained, such relative rapid operation of the armature andcontacts of a relay presents problems in the design and construction ofthe parts for reliable operation over long periods of time. For thepurpose of avoiding such continuing and rapid movement of contactingparts, the arrangement shown in Fig. 2 is proposed, in which the trackrail current energizes an organization of transformers and vacuum tubesin such a way that the same operation of the decoder relays R and R|80is accomplished without rapidly operating contacts.

Referring to Fig. 2, it is assumed that high frequency alternatingcurrent is supplied to the track rails by a coder or modulator at coderates of '75 or 180 times per minute in the same manner as alreadydescribed. At the entrance end of the block the input circuit of adouble-wave rectifier 4D is connected across the track rails, and itsoutput circuit is connected to the primary of a transformer 4|, so thatthis primary is energized with a substantially uni-direction of currentwhile the alternating current is applied to the track rails and isdeenergized when such rail current is cut off. The secondary of thetransformer 4| is divided into two halves which are connected in themanner shown to the input or grid circuits of two vacuum tubes of theusual three-element type. The plate circuits of these tubes areconnected to the two halves of the primary of a transformer 42, thesecondary of which is connected to rectifiers and decoder relays R15 andRIBO in the same manner as previously explained. When approach controlis desired, a relay, as TI is connected across the output circuit of therectifier 4D, and utilized to control the starting of the codingapparatus as previously explained in connection with Figs. 1 and 1A.

In this form of the invention however, the function of the track relaycontacts, such as contact 43 of relay T3 of Figs. 1 and 1A, is takenover by the tube hook-up, the coding relays RISU and R15 beingcontrolled by the tubes, and in turn controlling the wayside signals andthe application of coded current to the track block to the rear, exactlyas explained above in connection with Figs. 1 and 1A.

Considering the operation of this modified decoding equipment shown inFig. 2, when the track rail current is first applied, the voltageinduced in the secondary of the transformer 4| raises the grid potentialof one tube and lowers the grid potential of the other. This causescurrent to flow through the primary of the transformer 42 in onedirection in much the same manner as the closing of the front contact ofa code following track relay. When the rail current is cut off, avoltage of the opposite polarity is induced in the secondary of thetransformer 4|, reversing the relative potential of the grid circuitsand causing plate current to flow through the transformer 42 in theopposite direction. In this way, there is a pumping action through thetransformer 42 in substantially the same manner as is accomplished bythe closing of front and back contacts of a code following track relay.

As illustrated, the vacuum tubes are assumed to have substantially zerocurrent at zero grid potential for the plate voltage used; but thesetubes may be provided with a biasing grid potential. Also, these tubesare shown as of the simple conventional three-element type, with directcurrent for heating the filaments and the battery for the plate circuit;but tubes heated by alternating current, with rectified alternatingcurrent for the plate supply, and other types of thermionic devices maybe employed to perform the same functions.

The specific arrangement of parts shown and described is merely typicalof the nature of the invention; and various adaptations, modifications,and additions may be made without departing from the invention.

What I claim is:

1. In a system of signaling for railroads, the combination with aplurality of track circuits each having a track relay, of coding meansoperable to intermittently energize each of said track circuits withimpulses of distinctive code characteristics, decoding means associatedwith each track relay and responsive to the characteristic code impulsesenergizing that relay for controlling the code characteristics of thecurrent supplied to the track circuit in the rear, said coding meansbeing normally inactive, and means for initiating operation of thecoding means for a plurality of track circuits in advance of the oneoccupied by a train.

2. In a system of the character described, coding means forintermittently energizing each of a number of track circuits atdifferent rates with alternating current of a. distinctive frequency, anapproach control relay for initiating operation of each coding means,and means responsive to the presence of a train on a track circuit foractuating said approach control relays for a predetermined number oftrack circuits in advance.

3. A coded track circuit system for railroads comprising, in combinationwith a plurality of track circuits each having a code following trackrelay, a coding means associated with each circuit for supplying codedcurrent to the exit end of its circuit, normally inactive approachcontrol means for each track circuit operable to initiate operation ofthe coding means for its circuit, and means for actuating said approachcontrol means for a plurality of track circuits in advance of oneoccupied by a train.

4. In a system of the character described, a plurality of track circuitshaving code following track relays, decoding means including relaysselectively responsive to the rate of energization and deenergization ofeach track relay, coding means operable tointerrupt the supply ofcurrent to the track circuit in accordance with the COIL-r dition ofsaid decoder relays associated with: the block next in advance, saidcoding means being normally inactive, and means for initiating operationof the coding means for a plurality of track circuitsin advance of atrain.

5, In a coded track circuit system for railroads, a normally inactivecoding device associated'with each track circuit section and arranged,when active, to apply coded current to its section, an approach controlrelay at the exit end of each section for governing the operation of thecoding device for such section, and means responsive to thepresence ofatrain in any track section for operating said approach control relaysfor predetermined number of sections in advance of the occupied section.

6. In a coded track circuit system of the character described, thecombination with a plurality of track circuit sections and a normallyinactive coding device for each section for supplying coded current toits section, of means responsive to the presence of a train on any givensection for initiating operation of said coding devices for apredetermined number of track sections in ad- Vance of the occupiedsection.

'7. In a coded track circuit system of the character described, aplurality of track sections each having a track relay, a normallyinactive coding device associated with each section for supplyingcurrent impulses of different code characteristics to the track rails atthe exit end of that section, an approach control relay for each sectionacting when energized to initiate operation of the coding device forthat section, and means for energizing the approach control relay foreach section if any one of a plurality of track sections inthe rear ofsuch section is occupied by a train.

8. Ina coded track circuit system of the character described, aplurality of track sections each having a track relay, a coding devicefor each track section for at times supplying coded cur rent to itssection, an approach control relay at the exit end of each sectionacting when energized to cause operation of the coding device for suchsection, and line circuit means for energizing the approach controlrelay of each section and closed if the track relay of any one of aplurality'of sections in the rear of such section is deeenergized.

19. Ina coded track circuit system of the character described, aplurality of track sections each having a track relay, a coding devicefor each track section, an approach control relay at the exit end ofeach section acting when energized to cause operation of thecorresponding coding device, line circuit means for energizingthe'approach control relay of each section and closed if the track relayof any one of a plurality of sections in the rear thereof isde-energized, and decoding means, responsive to code from the codingdevice, comprising decoder relays, circuits eifective to energize saiddecoder relays only if the respective circuit is pulsed at apredetermined rate, and means including thermionic devices andresponsive to a difference of potential between the track rails forimpulsing said energizing circuits in accordance with the periodicity ofenergization of the track rails.

10. Decoding means for coded track circuits comprising, a transformer,decoding means including relays selectively responsive to the periodicyof the energization of said transformer, a local source of currentconnected to and directly energizing said transformer, and meansincluding vacuum tube devices responsive to a difference of potentialbetween the track rails for controlling the energization'of first oneportion of said transformer in one direction and. then the other portionof said transformer in the other direction.

11. In a decoding means for coded track circuits, a decodingtransformer, decoding means including relays selectively responsive tothe periodicity of the energization of the decoding transformer, a localsource of current, a receiving transformer having its primary connectedacross the coded circuit, thermionic devices connected respectively tothe two terminals of the secondary of the receiving transformer so as tocause their grids to be biased by the receiving transformer,.meansconnecting the local source of current between an intermediate point ofthe primary of the coding transformer and the two filaments of thethermionic devices, whereby to energize first one part of the codingtransformer primary, and then the other, in first one direction and thenin the other direction.

WADE H. REICHARD.

